Ventilation is used to control the build-up of airborne contaminants in order to reduce worker exposure and the potential for fire or explosion. The following provides examples of the types of ventilation commonly used to control airborne contaminants in manufacturing processes:
General or Dilution Ventilation
General ventilation works on the principle of removing and replacing contaminated air before chemical concentrations reach unacceptable levels. General ventilation should be designed to create directional (one-way) airflow within an area and carry contaminated air away from the breathing zone of workers.
General Ventilation works best when:
- Contaminant emissions are widely dispersed within the work area
- Exhaust openings are near the contaminant source
- The worker(s) is upstream of the contaminant
Local Exhaust Ventilation
Local exhaust ventilation is designed to mitigate specific (local) sources. Ventilation hoods or vents are used to capture and directly remove contaminated air from the source.
Local Ventilation works best when:
- Ventilation hoods or vents are located as close as possible to the source of contamination
- Worker(s) are positioned within the flow of contaminated air
- There are no strong cross-drafts (i.e. from floor or wall-mounted cooling fans)